; intended to work for WISE L1b headers, not sure if there are other different
; or more general types of SIP WCS that come from different data sets
; and/or telescopes

function unflatten_sip, astr_flat

  distort = struct_selecttags(astr_flat, select=['A', 'B', 'AP', 'BP'])

  addstr = {name: 'SIP'}

  distort = struct_addtags(addstr, distort)

  astr = struct_trimtags(astr_flat, except=['A', 'B', 'AP', 'BP'])

  addstr = {distort: distort}
  astr = struct_addtags(astr, addstr)

  return, astr
end